The stratigraphy, structure and mineralization of the Greenhow mining area, Yorkshire

Abstract

Summary The primary object of the work was the investigation of the geological environment of the galena-fluorite-barite deposits. The Carboniferous Limestone Series, over 1400 feet in maximum thickness, was mapped in six divisions covering faunal horizons from ?C 2 S 1 up to and possibly above D 2 . The Millstone Grit Series rests unconformably on horizons from the Davidsonina [ Cyrtina ] septosa band in D 1 up to beds with Orionastraea , the relations being ascribed to a pre-Millstone Grit uplift, possibly domal in form, accompanied by faulting. Within the Millstone Grit the "Top Limestone" (renamed the Cockhill Limestone) was proved to be characterized by Cravenoceras cowlingense (E 2 ). Two higher marine horizons, well known elsewhere, were established here by many exposures : the Colsterdale Marine Beds, characterized by Cravenoceras nitidum (E 2 ), seen in the same section as the Cockhill Limestone, and the glauconitic Cayton Gill Beds. A structure-contour map based on horizons in the Millstone Grit mapped at surface and underground shows that the anticline in the southern part of the area, trending east-north-east, has an amplitude of about 1000 feet, and that a series of domes and basins have been developed along its crest. The North Craven Fault, runniilg along the southern flank of the anticline, is a complex fracture-belt enclosing a tight syncline in the western part of the area, degenerating eastwards into a small strike-fault. The eastern half of the Bycliffe Vein-system is mineralized up to the Cayton Gill Beds but the remaining veins are mineralized only in the Carboniferous Limestone. The most important ore-shoots are found in the upper division of D l , in limestone underlying either shales low in the local D 2 or the basal shale of the Millstone Grit, depending on the position of the unconformity. Less important ore-shoots are found at various horizons from ?C 2 S 1 up to D 1 . It is suggested that extension of mineralization in depth beyond the limits so far revealed is possible in the case of ore-shoots related to shale overlying D 1 limestone. There is a crude zonal arrangement of minerals. Palaeontological notes are included on Hederella cf. chesterensis (of a suborder new to Britain) and on two new forms, Productus (Eomarginifera) tissingtonensis cambriensis and Eumorphoceras bisulcatum grassingtonensis .